Method of making tubes



April 19, 1932. "J, K, JAWSON I 1,854,550

METHOD 0? MAKING TUBES Filed Aug. 18, 1950 ?1- 1 19... INVENTOR wanna.

@mww' Patented Apr. 19, 1932 'rrao sr JOHN KENNETH JAMISON, 0F MONESSEN,PENNSYLVANIA, ASSIGNOB- TO PITTSBURGH STEEL PRODUCTS COMPANY, OFPITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA METHOD OF MAKINGTUBES Application filed. August 16, 1930. Serial No. 475,878.

My invention relates to a method of makin tubes, and particularly to themaking of tubes of very accurate dimensions and wall thickness, such astubes specially formed to serve as blanks for aeroplane propellers.

One object of my invention is to provide a method of making a tubularblank of tapered form which is accurate to predetermined dimensions inthe various portions thereof, and wherein there are no cracks or linesof weakness.

Another object of my invention is to provide a method of making atubular blank of tapered form which is accurate to predeterminedinternal dimensions.

Another object of my invention is to provide a blank that is of suchprecise dimensions that it can be shaped to form aeroplane propellersthat are accurately balanced.

Various ofthe steps followed in practising my invention are disclosed inthe accompanying drawings, wherein Figure 1 is a view showing a tubularblank at an initial stage; Fig. 2 is a view thereof showing its formfollowing a second step of my method; Fig. 3 shows its appearance at alater stage of operations; Fig. 4 is a view, on an enlarged scale,showing a preliminary shape imparted to the smaller end of the tube ofFig. 3; Fig. 5 is a view of the blank of Fig. 4 with its flared endreduced; Fig. 6 is a view showing the tube reduced to approximately itsfinally tapered form; Fig. 7 is a view showing a modifiation of theformation of the end portion of the tube shown in Figs. 4 and 5; Figs. 8to 13 show successive steps in the shaping of the larger end of thetube, and Fig. 14 shows the final step of imparting the desired internaldiameter to the tube.

While the blanks hereinafter are described as particularly designed foruse in the forming of aeroplane propellers, it will be understood thatthey may be employed in the making of various other articles where ahigh degree of accuracy of dimensions and distribution of weight isrequired.

Aeroplane propellers are frequently made of steel or a steel alloy orother hard metal, and difficulty is experienced in shaping these hardermetals to accurate desired contours,

particularly while cold, without developing lines of Weakness or cracksin the metal.

In Fig. l, I show a blank 15 that may be of nickel steel alloy or othersuitable metal. Starting with a cylindrical blank, the end portion A issubjected to a pressing operation in suitable dies to slightly flare andtaper the same. A second operation is then performed upon the blank toslightly taper it through out the portion marked B, in both cases theblank being flared slightly toward the left hand end thereof.

Fig. 3 shows the blank tapered still further, as indicated by the letterC, with that portion of the taper toward the small end of the tube beingon longitudinally curved lines.

In Fig. 4, which is on an enlarged scale, the small end 16 of the tubeof Fig. 3 is showna's expanded by a subsequent operation, with atapering or flaring effect that is tapered toward the body of the tubeand flared outwardly. This operation results in the thinning of the wallof the portion 16. Thereupon the said end portion 16 is reduced to itsoriginal diameter as shown in Fig. 3 (Fig. 5 being on an enlargedscale), the reduced wall thickness of Fig. 4 being preserved, such wallthickness, however, being tapered as shown in Fig. 5. The tapering ofthe wall at this point to the reduced wall thickness prevents theformation of longitudinal seams or transverse corrugations on the insideof the tube during cold or hot swaging or tapering, especially since thedegree of taper at this point is considerably greater than at otherpoints. v

The blank having the pre-formed wall portion C and the reduced wallportion 16 is then heated and shaped by a tapered die, to the contourshown in Fig. 6.

Instead of reducing and tapering the wall portion 16 in the mannerindicated by Figs. 4 and 5, l have shown in Fig. 7 another manner inwhich this portion, here designated as 16a, may be reduced, this methodinvolving in the grinding or cutting away of metal from the periphery ofthis smaller end of the tube. The blank of Fig. 7 may then be heated andshaped on a tapered die to the contour of Fig. 6.

In eithermethod of reducing and tapering the wall thickness of thesmaller end of the tube, the result is that in reducing the smaller endof the tube to the tapering form shown in Fig. 6, there is better andmore uniform distribution of the metal in such portion of the tube,which result would be impossible or difficult of attainment if the end16 of the blank were simply compressed to the tapered form shown in Fig.6. It will be seen that after each operation involving the steps shownin Figs. 3 and 6, the tube is elongated somewhat, by reason of thereduction in diameter of certain portions of the tube in producing thetapered shape.

The blank of Fig. 6 is then upset interiorly at its larger end bysuitable dies and an upsetting member, in successive stages, as shown inFigs. 8,-9 and 10.

The successive tages of internal upsetting gradually increa e the wallthickness of the larger end of the tube, the metal of the tube beingcompressed or forced inwardly with out the formation of cracks orwrinkles. The thickened mass of metal thus formed interiorly of the tubemay be readily transferred or expanded to form a thickened externalflange 17 on the tube.

Ordinarily, external thickening and upsetting of a thin-walled tube ofhardened metal, such as is here employed, results in the formation ofcracks and wrinkles, which I find can be eliminated by first thickeningand upsetting the metal internally, and then expanding the mass of metalradially to form an external flange.

Following the internal upsetting operations, suitable dies aresubstituted for the internal upsetting dies, and the mass of metal isexpanded and forced outwardly to form the external tapering flange 17,as shown in Fig. 11. Subsequently, the tapering flange of Fig. 11 isflattened and compressed longitudinally of the pipe to the shape shownin Figs. 12 and 13, in successive stages.

In most instances it will be found desirable to anneal the blank beforeexpanding it by a mandrel 20, so that it will have the necessaryhardness and need not again be annealed or heat-treated after it hasbeen shaped by the mandrel.

The blank of Figs. 1 to 13 is inserted through a tubular holder memberor block 18 and a supporting member 19, with the flange 17 in abuttingengagement with the end of the block 18. The tapered mandrel 20 is theninserted into the tube and is forced into the tube 15 to effect a finalexpanding operation and to bring the interior of the tube throughout itslength to the exact internal diameter desired for the completed blank.The distance which the mandrel 20 is inserted into the tube can bedetermined by a gage mark or marks 21. The mandrel will preferablybecoated with a lubricant, to reduce friction thereof with the tube.

All subsequent operations on the tube are performed on its exteriorsurface, and it is therefore highly important that the internaldimensions thereof be quite accurate in order to produce truly balancedblades. The tube, previous to its final expansion by the mandrel 20,preferably has its interior diameter slightly undersize, say inches, sothat there will be sutlicient expansion by the mandrel 20 to assure allthe metal of the tube taking a permanent set, and insuring accuracy ofinternal dimensions and smoothness of internal walls.

The tube may be of various wall thickness, and as an example of the gageof the metal with which the foregoing operations may be conducted, theblank of Fig. 1, may have an initial wall thickness of approximately.165 inches, while the wall thickness of the tube will be approximatelymaintained throughout the operations on the blank except for thetemporary thinning of the smaller end of they blank as in Figs. 4 and 7,and for the thickening of the'other end of the blank as in Figs. 8 to13.

After expansion of the tube by the mandrel 20, the mandrel is withdrawntherefrom, and the outer surface of the tube is ground to bring it to'the exact overall dimensions, and this grinding may be such that thewall thickness tapers toward the small end of the tube, since so greatthickness of metal is not required at such end as-at the base or largeend of the tube. The internal diameter of the tube being preciselyformed by the mandrel 20, it is a simple manner to so grind the exteriorsurface thereof as to provide the desired wall thickness and properdistribution of weight.

The small end of the tube is closed by a spinning operation, whereuponthe tube constitutes a completed blank ready for shaping to propellerform as by performing a squeezing operation. thereon, as betweenupsetting dies to flatten it somewhat or to give it a generally ovalshape in cross section.

I claim as my invention 1. The method of making propeller blanks oftubes having a hardness approximating that of nickel steel alloy, whichcomprises forming a tube to tapered form with an internal diameterslightly less than that desired for the completed blank, forming aninterior flange at the larger end of said blank, expanding the metalcomposing such flange to form an exterior flange, and introducing atapered mandrel into the blank to slightly expand the same.

2. The method of making propeller blanks of tubes having a hardnessapproximating that of nickel steel alloy, which comprises forming a tubeto tapered form with an internal diameter slightly less than thatdesired for the completed blank, forming an interior flange at thelarger end of said blank, expanding the metal composing such flange toform an exterior flange, introducing a tapered mandrel into the blank toslightly expand the same, and grinding the exterior surface of theblank.

3. The method of making propeller blanks of tubes having a hardnessapproximating that of nickel steel alloy, which comprises forming a tubeto tapered form with an internal diameter slightly less than thatdesired for the completed blank, forming an interior flange at thelarger end of said blank, expanding the metal composing such flange toform an exterior flange, introducing a tapered mandrel into the blank toslightly expand the same, and spinning the reduced end of the blank toclose said end.

4. The method of making tapered tubular metal blanks which comprisesfirst expanding the metal at that end of. the blank which is of reduceddiameter when completed, contracting said expanded end, the saidendbeingmaintained of circular form in cross section during expansion andcontraction thereof, and thereafter shaping the blank to its completedform.

5. The method of making tapered tubular metal blanks which comprisesfirst thinning the metal at that end of a blank which is of reduceddiameter when completed, contracting the said thinned end whilemaintaining it of circular form in cross section, and thereafter shapingthe blank to tapered form throughout substantially its entire length, bya tapered die introduced internally of the blank.

In testimony whereof I, the said JOHN KENNETH JAMIsoN, have hereunto setmy hand.

JOHN KENNETH J AMISON.

